I came home, and looked through the 'blue' section of the Collins Gem guide to Butterflies, and the underwing pattern of the Silver-studded Blue described in the book was the nearest pattern that matched the underwing of what I saw. The orange/blue trim as pictured in the book being complete all the way around the outer edge.
The book in question being this one:
http://www.nhmshop.co.uk/insect-and-spi ... oduct.htmlOf course, I might be wrong - would a 'butterfly specialist' be agreeable to perhaps coming to Frampton some time this month to help develop my knowledge? I'm available at weekends, and also on Tuesday, Wednesday and Friday afternoons.